U.S. patent number 7,916,108 [Application Number 12/106,599] was granted by the patent office on 2011-03-29 for liquid crystal display panel with color washout improvement and applications of same.
This patent grant is currently assigned to Au Optronics Corporation. Invention is credited to Chien-Hua Chen, Chih-Yuan Chien, Hsueh-Ying Huang, Chen-Kuo Yang.
United States Patent |
7,916,108 |
Yang , et al. |
March 29, 2011 |
Liquid crystal display panel with color washout improvement and
applications of same
Abstract
A liquid crystal display (LCD) panel with color washout
improvement. In one embodiment, the LCD panel a plurality of
pixels, {P.sub.n,m}, spatially arranged in the form of a matrix,
n=1, 2, . . . , N, and m=1, 2, . . . , M, and N, M being an integer
greater than zero, each pixel P.sub.n,m comprising at least a first
sub-pixel, P.sub.n,m(1), having a sub-pixel electrode and a second
sub-pixel, P.sub.n,m(2), having a sub-pixel electrode. The
plurality of pixels, {P.sub.n,m}, is configured such that when a
gray level voltage associated with a gray level, g, of an image to
be displayed on a pixel is applied to the pixel P.sub.n,m, a
potential difference, .DELTA.V.sub.12(g), is generated in the
sub-pixel electrodes of the first and second sub-pixels of the
pixel P.sub.n,m. The potential difference, .DELTA.V.sub.12(g)
varies with the gray level g of the image to be displayed on the
pixel, where g=0, 1, 2, . . . , R corresponding to one of the
shades of grey of the image expressed in h bits, h being an integer
greater than zero and R=(2.sup.h-1).
Inventors: |
Yang; Chen-Kuo (Hsinchu,
TW), Chen; Chien-Hua (Hsinchu, TW), Chien;
Chih-Yuan (Hsinchu, TW), Huang; Hsueh-Ying
(Hsinchu, TW) |
Assignee: |
Au Optronics Corporation
(Hsinchu, TW)
|
Family
ID: |
40537897 |
Appl.
No.: |
12/106,599 |
Filed: |
April 21, 2008 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20090262056 A1 |
Oct 22, 2009 |
|
Current U.S.
Class: |
345/89; 345/93;
345/88 |
Current CPC
Class: |
G09G
3/3648 (20130101); G09G 2310/0205 (20130101); G09G
2300/0426 (20130101); G02F 1/13624 (20130101); G02F
1/134345 (20210101); G09G 2320/028 (20130101); G09G
3/3607 (20130101) |
Current International
Class: |
G09G
3/36 (20060101) |
Field of
Search: |
;345/87-100,204-215,690 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Shankar; Vijay
Attorney, Agent or Firm: Xia; Tim Tingkang Morris, Manning
& Martin, LLP
Claims
What is claimed is:
1. A liquid crystal display (LCD) panel, comprising: a. a common
electrode; b. a plurality of scanning lines, {G.sub.n}, n=1, 2, . .
. , N, spatially arranged along a row direction; c. a plurality of
data lines, {D.sub.m}, m=1, 2, . . . , M, spatially arranged
crossing the plurality of scanning lines {G.sub.n} along a column
direction perpendicular to the row direction; and d. a plurality of
pixels, {P.sub.n,m}, spatially arranged in the form of a matrix,
each pixel P.sub.n,m defined between two neighboring scanning lines
G.sub.n and G.sub.n+1 and two neighboring data lines D.sub.m and
D.sub.m+1, and comprising at least a first sub-pixel, P.sub.n,m(1),
and a second sub-pixel, P.sub.n,m(2), wherein each of the first
sub-pixel P.sub.n,m(1) and the second sub-pixel P.sub.n,m(2)
comprises a sub-pixel electrode, a liquid crystal (LC) capacitor
and a storage capacitor both electrically connected between the
sub-pixel electrode and the common electrode in parallel, and a
transistor having a gate electrically connected to the scanning
line G.sub.n, a source electrically connected to the sub-pixel
electrode and a drain, and wherein the drain of the transistor of
the first sub-pixel P.sub.n,m(1) of the pixel P.sub.n,m is
electrically connected to the data line D.sub.m, and the drain of
the transistor of the second sub-pixel P.sub.n,m(2) of the pixel
P.sub.n,m is electrically connected to the sub-pixel electrode of
the first sub-pixel P.sub.k,m(1) of the pixel P.sub.k,m, or wherein
the drain of the transistor of the second sub-pixel P.sub.n,m(2) of
the pixel P.sub.n,m is electrically connected to the data line
D.sub.m, and the drain of the transistor of the first sub-pixel
P.sub.n,m(1) of the pixel P.sub.n,m is electrically connected to
the sub-pixel electrode of the second sub-pixel P.sub.k,m(2) of the
pixel P.sub.k,m, wherein k=1, 2, . . . , N, and k.noteq.n, wherein
when a scanning signal is applied to a scanning line G.sub.a to
turn on the corresponding transistors connected to the scanning
line G.sub.n, a plurality of data signals is simultaneously applied
to the plurality of data lines {D.sub.n}, respectively, so as to
charge the corresponding LC capacitors and storage capacitors of
each pixel of the corresponding pixel row for aligning states of
corresponding liquid crystal cells associated with the pixel row to
control light transmittance therethrough.
2. The LCD panel of claim 1, wherein the plurality of data signals
comprises a plurality of gray level voltages, each gray level
voltage being associated with a gray level, g, of an image to be
displayed on a pixel in the pixel row such that when the gray level
voltage is applied the pixel, a potential difference,
.DELTA.V.sub.12(g), is generated in the sub-pixel electrodes of the
first and second sub-pixels of the pixel, which varies with the
gray level g of the image to be displayed on the pixel, wherein
g=0, 1, 2, . . . , R corresponding to one of the shades of grey of
the image expressed in h bits, h being an integer greater than zero
and R=(2.sup.h-1).
3. The LCD panel of claim 2, wherein a. when the gray level g is in
the range from 0 to g.sub.a, the potential difference
.DELTA.V.sub.12(g) for the gray level g is less than the potential
difference .DELTA.V.sub.12(g+1) for the gray level (g+1); and b.
when the gray level g is in the range from g.sub.b to R, the
potential difference .DELTA.V.sub.12(g) for the gray level g is
greater than the potential difference .DELTA.V.sub.12(g+1) for the
gray level (g+1), wherein 0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a
and g.sub.b each being an integer greater than zero.
4. The LCD panel of claim 2, wherein a. when the gray level g is in
the range from 0 to g.sub.a, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.a; b. when the gray level g is in the range from g.sub.a to
g.sub.b, the potential difference .DELTA.V.sub.12(g) for the gray
level g has a constant voltage, V.sub.b; and c. when the gray level
g is in the range from g.sub.b to R, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.c, wherein 0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and
g.sub.b each being an integer greater than zero, and wherein
V.sub.a>V.sub.b>V.sub.c.
5. The LCD panel of claim 1, wherein k=n+1 or n-1.
6. The LCD panel of claim 1, wherein the sub-pixel electrode of the
first sub-pixel has an area A1, and the sub-pixel electrode of the
second sub-pixel has an area A2, and wherein the ratio of A1/A2 is
in a range of about 0.2-5.0.
7. A method of driving a liquid crystal display (LCD) with color
washout improvement, comprising the steps of: a. providing an LCD
panel comprising: (i). a common electrode; (ii). a plurality of
scanning lines, {G}, n=1, 2, . . . , N, spatially arranged along a
row direction; (iii). a plurality of data lines, {D.sub.m}, m=1, 2,
. . . , M, spatially arranged crossing the plurality of scanning
lines {G.sub.n} along a column direction perpendicular to the row
direction; and (iv). a plurality of pixels, {P.sub.n,m}, spatially
arranged in the form of a matrix, each pixel P.sub.n,m defined
between two neighboring scanning lines G.sub.n and G.sub.n+1 and
two neighboring data lines D.sub.m and D.sub.m+1, and comprising at
least a first sub-pixel, P.sub.n,m(1), and a second sub-pixel,
P.sub.n,m(2), wherein each of the first sub-pixel P.sub.n,m(1) and
the second sub-pixel P.sub.n,m(2) comprises a sub-pixel electrode,
a liquid crystal (LC) capacitor and a storage capacitor both
electrically connected between the sub-pixel electrode and the
common electrode in parallel, and a transistor having a gate
electrically connected to the scanning line G.sub.n, a source
electrically connected to the sub-pixel electrode and a drain,
wherein the drain of the transistor of the first sub-pixel
P.sub.n,m(a) of the pixel P.sub.n,m is electrically connected to
the data line D.sub.m, and the drain of the transistor of the
second sub-pixel P.sub.n,m(2) of the pixel P.sub.n,m is
electrically connected to the sub-pixel electrode of the first
sub-pixel P.sub.k,m(1) of the pixel P.sub.k,m, or wherein the drain
of the transistor of the second sub-pixel P.sub.n,m(2) of the pixel
P.sub.n,m is electrically connected to the data line D.sub.m, and
the drain of the transistor of the first sub-pixel P.sub.n,m(1) of
the pixel P.sub.n,m is electrically connected to the sub-pixel
electrode of the second sub-pixel P.sub.k,m(2) of the pixel
P.sub.k,m, wherein k=1, 2, . . . , N, and k.noteq.n; and b.
applying a plurality of driving signals to the LCD panel so as to
generate a potential difference, .DELTA.V.sub.12(g), in the
sub-pixel electrodes of the first and second sub-pixels of each
pixel, respectively.
8. The method of claim 7, further comprising the step of generating
the plurality of driving signals.
9. The method of claim 8, wherein the plurality of driving signals
comprises a plurality of scanning signals sequentially applied to
the plurality of scanning lines, a plurality of data signals
simultaneously applied to the plurality of data lines, and a common
signal applied to the common electrode, respectively.
10. The method of claim 9, wherein the plurality of data signals
comprises a plurality of gray level voltages, each gray level
voltage being associated with a gray level, g, of an image to be
displayed on a pixel in the pixel row such that when the gray level
voltage is applied the pixel, the potential difference
.DELTA.V.sub.12(g) generated in the sub-pixel electrodes of the
first and second sub-pixels of the pixel varies with the gray level
g of the image to be displayed on the pixel, wherein g=0, 1, 2, . .
. , R corresponding to one of the shades of grey of the image
expressed in h bits, h being an integer greater than zero and
R=(2.sup.h-1).
11. The method of claim 10, wherein a. when the gray level g is in
the range from 0 to g.sub.a, the potential difference
.DELTA.V.sub.12(g) for the gray level g is less than the potential
difference .DELTA.V.sub.12(g+1) for the gray level (g+1); and b.
when the gray level g is in the range from g.sub.b to R, the
potential difference .DELTA.V.sub.12(g) for the gray level g is
greater than the potential difference .DELTA.V.sub.12(g+1) for the
gray level (g+1), wherein 0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a
and g.sub.b each being an integer greater than zero.
12. The method of claim 10, wherein a. when the gray level g is in
the range from 0 to g.sub.a, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.a; b. when the gray level g is in the range from g.sub.a to
g.sub.b, the potential difference .DELTA.V.sub.12(g) for the gray
level g has a constant voltage, V.sub.b; and c. when the gray level
g is in the range from g.sub.b to R, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.c, wherein 0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and
g.sub.b each being an integer greater than zero, and wherein
V.sub.a>V.sub.b>V.sub.c.
13. A liquid crystal display (LCD) panel, comprising: a. a
plurality of pixels, {P.sub.n,m}, spatially arranged in the form of
a matrix, n=1, 2, . . . , N, and m=1, 2, . . . , M, and N, M being
an integer greater than zero, each pixel P.sub.n,m comprising at
least a first sub-pixel, P.sub.n,m(1), having a sub-pixel
electrode, and a second sub-pixel, P.sub.n,m(2), having a sub-pixel
electrode, wherein the plurality of pixels {P.sub.n,m} is
configured such that when a gray level voltage associated with a
gray level, g, of an image to be displayed on a pixel P.sub.n,m is
applied to the pixel P.sub.n,m, a potential difference,
.DELTA.V.sub.12(g), is generated in the sub-pixel electrodes of the
first and second sub-pixels of the pixel P.sub.n,m, and varies with
the gray level g, such that (i). when the gray level g is in the
range from 0 to g.sub.a, the potential difference
.DELTA.V.sub.12(g) for the gray level g is less than the potential
difference .DELTA.V.sub.12(g+1) for the gray level (g+1); and (ii).
when the gray level g is in the range from g.sub.b to R, the
potential difference .DELTA.V.sub.12(g) for the gray level g is
greater than the potential difference .DELTA.V.sub.12(g+1) for the
gray level (g+1), wherein g=0, 1, 2, . . . , R corresponding to one
of the shades of grey of the image expressed in h bits, h being an
integer greater than zero and R=(2.sup.h-1), and wherein
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero.
14. The LCD panel of claim 13, further comprising: a. a common
electrode; b. a plurality of scanning lines, {G.sub.n}, n=1, 2, . .
. , N, spatially arranged along a row direction; and c. a plurality
of data lines, {D.sub.m}, m=1, 2, . . . , M, spatially arranged
crossing the plurality of scanning lines {G.sub.n} along a column
direction perpendicular to the row direction, wherein each pixel
P.sub.n,m of the plurality of pixels {P.sub.n,m} is defined between
two neighboring scanning lines G.sub.n and G.sub.n+1 and two
neighboring data lines D.sub.m and D.sub.m+1.
15. The LCD panel of claim 14, wherein each of the first sub-pixel
P.sub.n,m(1) and the second sub-pixel P.sub.n,m(2) of each pixel
P.sub.n,m further comprises a liquid crystal (LC) capacitor and a
storage capacitor both electrically connected between the sub-pixel
electrode and the common electrode in parallel, and a transistor
having a gate electrically connected to the scanning line G.sub.n,
a source electrically connected to the sub-pixel electrode and a
drain.
16. The LCD panel of claim 15, wherein the drain of the transistor
of the first sub-pixel P.sub.n,m(1) of the pixel P.sub.n,m is
electrically connected to the data line D.sub.m, and the drain of
the transistor of the second sub-pixel P.sub.n,m(2) of the pixel
P.sub.n,m is electrically connected to the sub-pixel electrode of
the first sub-pixel P.sub.k,m(1) of the pixel P.sub.k,m, wherein
k=1, 2, . . . , N, and k.noteq.n.
17. The LCD panel of claim 15, wherein the drain of the transistor
of the second sub-pixel P.sub.n,m(2) of the pixel P.sub.n,m is
electrically connected to the data line D.sub.m, and the drain of
the transistor of the first sub-pixel P.sub.n,m(1) of the pixel
P.sub.n,m is electrically connected to the sub-pixel electrode of
the second sub-pixel P.sub.k,m(2) of the pixel P.sub.k,m, wherein
k=1, 2, . . . , N, and k.noteq.n.
18. A liquid crystal display (LCD) panel, comprising: a. a
plurality of pixels, {P.sub.n,m}, spatially arranged in the form of
a matrix, n=1, 2, . . . , N, and m=1, 2, . . . , M, and N, M being
an integer greater than zero, each pixel P.sub.n,m comprising at
least a first sub-pixel, P.sub.n,m(1), having a sub-pixel electrode
and a second sub-pixel, P.sub.n,m(2), having a sub-pixel electrode,
wherein the plurality of pixels {P.sub.n,m} is configured such that
when a gray level voltage associated with a gray level, g, of an
image to be displayed on a pixel is applied to the pixel P.sub.n,m,
a potential difference, .DELTA.V.sub.12(g), is generated in the
sub-pixel electrodes of the first and second sub-pixels of the
pixel P.sub.n,m, and varies with the gray level g, such that (i).
when the gray level g is in the range from 0 to g.sub.a, the
potential difference .DELTA.V.sub.12(g) for the gray level g has a
constant voltage, V.sub.a; (ii). when the gray level g is in the
range from g.sub.a to g.sub.b, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.b; and (iii). when the gray level g is in the range from
g.sub.b to R, the potential difference .DELTA.V.sub.12(g) for the
gray level g has a constant voltage, V.sub.c, wherein g=0, 1, 2, .
. . , R corresponding to one of the shades of grey of the image
expressed in h bits, h being an integer greater than zero and
R=(2.sup.h-1), wherein 0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a
and g.sub.b each being an integer greater than zero, and wherein
V.sub.a>V.sub.b>V.sub.c.
19. A liquid crystal display (LCD) panel, comprising: a. a
plurality of pixels, {P.sub.n,m}, spatially arranged in the form of
a matrix, n=1, 2, . . . , N, and m=1, 2, . . . , M, and N, M being
an integer greater than zero, each pixel P.sub.n,m comprising at
least a first sub-pixel, P.sub.n,m(1), having a sub-pixel
electrode, and a second sub-pixel, P.sub.n,m(2), having a sub-pixel
electrode, wherein the plurality of pixels, {P.sub.n,m}, is
configured such that when a gray level voltage associated with a
gray level, g, of an image to be displayed on a pixel is applied to
the pixel P.sub.n,m, a potential difference, .DELTA.V.sub.12(g), is
generated in the sub-pixel electrodes of the first and second
sub-pixels of the pixel P.sub.n,m, which varies with the gray level
g of the image to be displayed on the pixel, wherein g=0, 1, 2, . .
. , R corresponding to one of the shades of grey of the image
expressed in h bits, h being an integer greater than zero and
R=(2.sup.h-1).
20. The LCD panel of claim 19, wherein a. when
0.ltoreq.g.ltoreq.g.sub.a,
.DELTA.V.sub.12(g)<.DELTA.V.sub.12(g+1); and b. when
g.sub.b.ltoreq.g.ltoreq.R,
.DELTA.V.sub.12(g)>.DELTA.V.sub.12(g+1), wherein
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero.
21. The LCD panel of claim 19, wherein a. when
0.ltoreq.g.ltoreq.g.sub.a, .DELTA.V.sub.12(g)=V.sub.a; b. when
g.sub.a.ltoreq.g.ltoreq.g.sub.b, .DELTA.V.sub.12(g)=V.sub.b; and c.
when g.sub.b.ltoreq.g.ltoreq.R, .DELTA.V.sub.12(g)=V.sub.c, wherein
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero, and wherein V.sub.a, V.sub.b and V.sub.c
are constant voltages with V.sub.a>V.sub.b>V.sub.c.
22. A method of driving a liquid crystal display (LCD) with color
washout improvement, comprising the steps of: a. providing an LCD
panel comprising a plurality of pixels, {P.sub.n,m}, spatially
arranged in the form of a matrix, n=1, 2, . . . , N, and m=1, 2, .
. . , M, and N, M being an integer greater than zero, each pixel
P.sub.n,m comprising at least a first sub-pixel, P.sub.n,m(1),
having a sub-pixel electrode, and a second sub-pixel, P.sub.n,m(2),
having a sub-pixel electrode; and b. applying a plurality of
driving signals to the LCD panel so as to generate potential
difference, .DELTA.V.sub.12(g), in the sub-pixel electrodes of the
first and second sub-pixels of each pixel, respectively, which
varies with a gray level g of an image to be displayed on the
pixel, wherein g=0, 1, 2, . . . , R corresponding to one of the
shades of grey of the image expressed in h bits, h being an integer
greater than zero and R=(2.sup.h-1).
23. The method of claim 22, wherein b. when
0.ltoreq.g.ltoreq.g.sub.a,
.DELTA.V.sub.12(g)<.DELTA.V.sub.12(g+1); and c. when
g.sub.b.ltoreq.g.ltoreq.R,
.DELTA.V.sub.12(g)>.DELTA.V.sub.12(g+1), wherein
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero.
24. The method of claim 22, wherein a. when
0.ltoreq.g.ltoreq.g.sub.a, .DELTA.V.sub.12(g)=V.sub.a; b. when
g.sub.a.ltoreq.g.ltoreq.g.sub.b, .DELTA.V.sub.12(g)=V.sub.b; and c.
when g.sub.b.ltoreq.g.ltoreq.R, .DELTA.V.sub.12(g)=V.sub.c, wherein
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero, and wherein V.sub.a, V.sub.b and V.sub.c
are constant voltages with V.sub.a>V.sub.b>V.sub.c.
25. The method of claim 22, further comprising the step of
generating the plurality of driving signals.
Description
FIELD OF THE INVENTION
The present invention relates generally to a liquid crystal display
(LCD), and more particularly to an LCD apparatus having an LCD
panel with color washout improvement.
BACKGROUND OF THE INVENTION
Liquid crystal displays (LCDs) are commonly used as a display
device because of its capability of displaying images with good
quality while using little electrical power. An LCD apparatus
includes an LCD panel formed with liquid crystal cells and pixel
elements with each associating with a corresponding liquid crystal
cell and having a liquid crystal (LC) capacitor and a storage
capacitor, a thin film transistor (TFT) electrically coupled with
the liquid crystal capacitor and the storage capacitor. These pixel
elements are substantially arranged in the form of a matrix having
a number of pixel rows and a number of pixel columns. Typically,
scanning signals are sequentially applied to the number of pixel
rows for sequentially turning on the pixel elements row-by-row.
When a scanning signal is applied to a pixel row to turn on
corresponding TFTs of the pixel elements of a pixel row, source
signals (image signals) for the pixel row are simultaneously
applied to the number of pixel columns so as to charge the
corresponding liquid crystal capacitor and storage capacitor of the
pixel row for aligning orientations of the corresponding liquid
crystal cells associated with the pixel row to control light
transmittance therethrough. By repeating the procedure for all
pixel rows, all pixel elements are supplied with corresponding
source signals of the image signal, thereby displaying the image
signal thereon.
Liquid crystal molecules have a definite orientational alignment as
a result of their long, thin shapes. The orientations of liquid
crystal molecules in liquid crystal cells of an LCD panel play a
crucial role in the transmittance of light therethrough. For
example, in a twist nematic LCD, when the liquid crystal molecules
are in its tilted orientation, light from the direction of
incidence is subject to various different indexes of reflection.
Since the functionality of LCDs is based on the birefringence
effect, the transmittance of light will vary with different viewing
angles. Due to such differences in light transmission, optimum
viewing of an LCD is limited within a narrow viewing angle. The
limited viewing angle of LCDs is one of the major disadvantages
associated with the LCDs and is a major factor in restricting
applications of the LCDs.
Several approaches exist for increasing the viewing angles of LCDs,
such as in-plane switching (IPS) mode, and multi-domain vertical
alignments. IPS mode uses comb-like inter-digitized electrodes to
apply electrical fields in the plane of the substrates, thereby
aligning the liquid crystal molecules along the substrates and
providing wide viewing angles for use in wide viewing angle
monitors or other applications. However, although IPS provides wide
viewing angles, it requires high voltages and has low aperture
ratios. In addition, due to the planar electric field structure,
IPS mode inherently suffers from severe image sticking. A
multi-domain arrangement is achieved by introducing a protruding
structure that forces the liquid crystal molecules to tilt in
different directions. However, such a multi-domain vertical
alignment requires an extra photolithography step during
fabrication.
Therefore, a heretofore unaddressed need exists in the art to
address the aforementioned deficiencies and inadequacies.
SUMMARY OF THE INVENTION
The present invention, in one aspect, relates to an LCD panel with
color washout improvement. In one embodiment, the LCD panel
includes a common electrode; a plurality of scanning lines,
{G.sub.n}, n=1, 2, . . . , N, spatially arranged along a row
direction; a plurality of data lines, {D.sub.m}, m=1, 2, . . . , M,
spatially arranged crossing the plurality of scanning lines
{G.sub.n} along a column direction perpendicular to the row
direction; and a plurality of pixels, {P.sub.n,m}, spatially
arranged in the form of a matrix, each pixel P.sub.n,m defined
between two neighboring scanning lines G.sub.n and G.sub.n+1 and
two neighboring data lines D.sub.m and D.sub.m+1. Each pixel
P.sub.n,m comprises at least a first sub-pixel, P.sub.n,m(1), and a
second sub-pixel, P.sub.n,m(2). Each of the first sub-pixel
P.sub.n,m(1) and the second sub-pixel P.sub.n,m(2) comprises a
sub-pixel electrode, a liquid crystal (LC) capacitor and a storage
capacitor both electrically connected between the sub-pixel
electrode and the common electrode in parallel, and a transistor
having a gate electrically connected to the scanning line G.sub.n,
a source electrically connected to the sub-pixel electrode and a
drain.
In one embodiment, the drain of the transistor of the first
sub-pixel P.sub.n,m(1) of the pixel P.sub.n,m is electrically
connected to the data line D.sub.m, and the drain of the transistor
of the second sub-pixel P.sub.n,m(2) of the pixel P.sub.n,m is
electrically connected to the sub-pixel electrode of the first
sub-pixel P.sub.k,m(1) of the pixel P.sub.k,m, where k=1, 2, . . .
, N, and k.noteq.n. For example, k=n+1 or n-1.
In another embodiment, the drain of the transistor of the second
sub-pixel P.sub.n,m(2) of the pixel P.sub.n,m is electrically
connected to the data line D.sub.m, and the drain of the transistor
of the first sub-pixel P.sub.n,m(1) of the pixel P.sub.n,m is
electrically connected to the sub-pixel electrode of the second
sub-pixel P.sub.k,m(2) of the pixel P.sub.k,m, where k=1, 2, . . .
N, and k.noteq.n. In one embodiment, k=n+1 or n-1.
In one embodiment, the sub-pixel electrode of the first sub-pixel
P.sub.n,m(1) of the pixel P.sub.n,m has an area A1, and the
sub-pixel electrode of the second sub-pixel P.sub.n,m(2) of the
pixel P.sub.n,m has an area A2, and the ratio of A1/A2 is in a
range of about 0.2-5.0.
For such an LCD panel, when a scanning signal is applied to a
scanning line G.sub.n to turn on the corresponding transistors
connected to the scanning line G.sub.n, a plurality of data signals
is simultaneously applied to the plurality of data lines {D.sub.n},
respectively, so as to charge the corresponding LC capacitors and
storage capacitors of each pixel of the corresponding pixel row for
aligning states of corresponding liquid crystal cells associated
with the pixel row to control light transmittance therethrough.
The plurality of data signals comprises a plurality of gray level
voltages, each gray level voltage being associated with a gray
level, g, of an image to be displayed on a pixel in the pixel row
such that when the gray level voltage is applied the pixel, a
potential difference, .DELTA.V.sub.12(g), is generated in the
sub-pixel electrodes of the first and second sub-pixels of the
pixel, which varies with the gray level g of the image to be
displayed on the pixel, where g=0, 1, 2, . . . , R corresponding to
one of the shades of grey of the image expressed in h bits, h being
an integer greater than zero and R=(2.sup.h-1).
In one embodiment, the potential difference .DELTA.V.sub.12(g)
generated in the sub-pixel electrodes of the first and second
sub-pixels of a pixel varies with the gray level g, such that (i)
when the gray level g is in the range from 0 to g.sub.a, the
potential difference .DELTA.V.sub.12(g) for the gray level g is
less than the potential difference .DELTA.V.sub.12(g+1) for the
gray level (g+1); and (ii) when the gray level g is in the range
from g.sub.b to R, the potential difference .DELTA.V.sub.12(g) for
the gray level g is greater than the potential difference
.DELTA.V.sub.12(g+1) for the gray level (g+1), where
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero.
In another embodiment, the potential difference .DELTA.V.sub.12(g)
varies with the gray level g, such that (i) when the gray level g
is in the range from 0 to g.sub.a, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.c; (ii) when the gray level g is in the range from g.sub.a to
g.sub.b, the potential difference .DELTA.V.sub.12(g) for the gray
level g has a constant voltage, V.sub.b; and (iii) when the gray
level g is in the range from g.sub.b to R, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.c, where V.sub.a>V.sub.b>V.sub.c.
In another aspect, the present invention relates to a method of
driving a liquid crystal display (LCD) with color washout
improvement. In one embodiment, the method includes the step of
providing an LCD panel. The LCD panel has a common electrode; a
plurality of scanning lines, {G.sub.n}, n=1, 2, . . . , N,
spatially arranged along a row direction; a plurality of data
lines, {D.sub.m}, m=1, 2, . . . , M, spatially arranged crossing
the plurality of scanning lines {G.sub.n} along a column direction
perpendicular to the row direction; and a plurality of pixels,
{P.sub.n,m}, spatially arranged in the form of a matrix. Each pixel
P.sub.n,m is defined between two neighboring scanning lines G.sub.n
and G.sub.n+1 and two neighboring data lines D.sub.m and D.sub.m+1.
Each pixel P.sub.n,m includes at least a first sub-pixel,
P.sub.n,m(1), and a second sub-pixel, P.sub.n,m(2), where each of
the first sub-pixel P.sub.n,m(1) and the second sub-pixel
P.sub.n,m(2) comprises a sub-pixel electrode, a liquid crystal (LC)
capacitor and a storage capacitor both electrically connected
between the sub-pixel electrode and the common electrode in
parallel, and a transistor having a gate electrically connected to
the scanning line G.sub.n, a source electrically connected to the
sub-pixel electrode and a drain.
In one embodiment, the drain of the transistor of the first
sub-pixel P.sub.n,m(a) of the pixel P.sub.n,m is electrically
connected to the data line D.sub.m, and the drain of the transistor
of the second sub-pixel P.sub.n,m(2) of the pixel P.sub.n,m is
electrically connected to the sub-pixel electrode of the first
sub-pixel P.sub.k,m(1) of the pixel P.sub.k,m. In another
embodiment, the drain of the transistor of the second sub-pixel
P.sub.n,m(2) of the pixel P.sub.n,m is electrically connected to
the data line D.sub.m, and the drain of the transistor of the first
sub-pixel P.sub.n,m(1) of the pixel P.sub.n,m is electrically
connected to the sub-pixel electrode of the second sub-pixel
P.sub.k,m(2) of the pixel P.sub.k,m, where k=1, 2, . . . , N, and
k.noteq.n.
Furthermore, the method includes the steps of generating the
plurality of driving signals; and applying a plurality of driving
signals to the LCD panel so as to generate a potential difference,
.DELTA.V.sub.12(g), in the sub-pixel electrodes of the first and
second sub-pixels of each pixel, respectively. In one embodiment,
the plurality of driving signals comprises a plurality of scanning
signals sequentially applied to the plurality of scanning lines, a
plurality of data signals simultaneously applied to the plurality
of data lines, and a common signal applied to the common electrode,
respectively.
In one embodiment, the plurality of data signals comprises a
plurality of gray level voltages. Each gray level voltage is
associated with a gray level, g, of an image to be displayed on a
pixel in the pixel row. When the gray level voltage is applied the
pixel, the potential difference .DELTA.V.sub.12(g) generated in the
sub-pixel electrodes of the first and second sub-pixels of the
pixel varies with the gray level g of the image to be displayed on
the pixel, where g=0, 1, 2, . . . , R corresponding to one of the
shades of grey of the image expressed in h bits, h being an integer
greater than zero and R=(2.sup.h-1).
In one embodiment, the potential difference .DELTA.V.sub.12(g)
generated in the sub-pixel electrodes of the first and second
sub-pixels of a pixel varies with the gray level g, such that (i)
when the gray level g is in the range from 0 to g.sub.a, the
potential difference .DELTA.V.sub.12(g) for the gray level g is
less than the potential difference .DELTA.V.sub.12(g+1) for the
gray level (g+1); and (ii) when the gray level g is in the range
from g.sub.b to R, the potential difference .DELTA.V.sub.12(g) for
the gray level g is greater than the potential difference
.DELTA.V.sub.12(g+1) for the gray level (g+1), where
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero.
In another embodiment, the potential difference .DELTA.V.sub.12(g)
varies with the gray level g, such that (i) when the gray level g
is in the range from 0 to g.sub.a, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.a; (ii) when the gray level g is in the range from g.sub.a to
g.sub.b, the potential difference .DELTA.V.sub.12(g) for the gray
level g has a constant voltage, V.sub.b; and (iii) when the gray
level g is in the range from g.sub.b to R, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.c, where V.sub.a>V.sub.b>V.sub.c.
In yet another aspect, the present invention relates to an LCD
panel. In one embodiment, the LCD panel has a plurality of pixels,
{P.sub.n,m}, spatially arranged in the form of a matrix, n=1, 2, .
. . , N, and m=1, 2, . . . , M, and N, M being an integer greater
than zero, each pixel P.sub.n,m comprising at least a first
sub-pixel, P.sub.n,m(1), having a sub-pixel electrode, and a second
sub-pixel, P.sub.n,m(2), having a sub-pixel electrode.
In one embodiment, the plurality of pixels {P.sub.n,m} is
configured such that when a gray level voltage associated with a
gray level, g, of an image to be displayed on a pixel P.sub.n,m is
applied to the pixel P.sub.n,m, a potential difference,
.DELTA.V.sub.12(g), is generated in the sub-pixel electrodes of the
first and second sub-pixels of the pixel P.sub.n,m, and varies with
the gray level g, such that (i) when the gray level g is in the
range from 0 to g.sub.a, the potential difference
.DELTA.V.sub.12(g) for the gray level g is less than the potential
difference .DELTA.V.sub.12(g+1) for the gray level (g+1); and (ii)
when the gray level g is in the range from g.sub.b to R, the
potential difference .DELTA.V.sub.12(g) for the gray level g is
greater than the potential difference .DELTA.V.sub.12(g+1) for the
gray level (g+1). g=0, 1, 2, . . . , R corresponding to one of the
shades of grey of the image expressed in h bits, h is an integer
greater than zero and R=(2.sup.h-1). Additionally,
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero.
The LCD panel also has a common electrode; a plurality of scanning
lines, {G.sub.n}, n=1, 2, . . . , N, spatially arranged along a row
direction; and a plurality of data lines, {D.sub.m}, m=1, 2, . . .
, M, spatially arranged crossing the plurality of scanning lines
{G.sub.n} along a column direction perpendicular to the row
direction, where each pixel P.sub.n,m of the the plurality of
pixels {P.sub.n,m} is defined between two neighboring scanning
lines G.sub.n and G.sub.n+1 and two neighboring data lines D.sub.m
and D.sub.m+1.
In one embodiment, each of the first sub-pixel P.sub.n,m(1) and the
second sub-pixel P.sub.n,m(2) of each pixel P.sub.n,m further
comprises a liquid crystal (LC) capacitor and a storage capacitor
both electrically connected between the sub-pixel electrode and the
common electrode in parallel, and a transistor having a gate
electrically connected to the scanning line G.sub.n, a source
electrically connected to the sub-pixel electrode and a drain. In
one embodiment, the drain of the transistor of the first sub-pixel
P.sub.n,m(a) of the pixel P.sub.n,m is electrically connected to
the data line D.sub.m, and the drain of the transistor of the
second sub-pixel P.sub.n,m(2) of the pixel P.sub.n,m is
electrically connected to the sub-pixel electrode of the first
sub-pixel P.sub.k,m(1) of the pixel P.sub.k,m. In another
embodiment, the drain of the transistor of the second sub-pixel
P.sub.n,m(2) of the pixel P.sub.n,m is electrically connected to
the data line D.sub.m, and the drain of the transistor of the first
sub-pixel P.sub.n,m(1) of the pixel P.sub.n,m is electrically
connected to the sub-pixel electrode of the second sub-pixel
P.sub.k,m(2) of the pixel P.sub.k,m. k=1, 2, . . . , N, and
k.noteq.n.
In a further aspect, the present invention relates to an LCD panel.
In one embodiment, the LCD panel includes a plurality of pixels,
{P.sub.n,m}, spatially arranged in the form of a matrix, n=1, 2, .
. . , N, and m=1, 2, . . . , M, and N, M being an integer greater
than zero, each pixel P.sub.n,m comprising at least a first
sub-pixel, P.sub.n,m(1), having a sub-pixel electrode, and a second
sub-pixel, P.sub.n,m(2), having a sub-pixel electrode. The
plurality of pixels {P.sub.n,m} is configured such that when a gray
level voltage associated with a gray level, g, of an image to be
displayed on a pixel is applied to the pixel P.sub.n,m, a potential
difference, .DELTA.V.sub.12(g), is generated in the sub-pixel
electrodes of the first and second sub-pixels of the pixel
P.sub.n,m, and varies with the gray level g, such that (i) when the
gray level g is in the range from 0 to g.sub.3, the potential
difference .DELTA.V.sub.12(g) for the gray level g has a constant
voltage, V.sub.3; (ii) when the gray level g is in the range from
g.sub.3 to g.sub.ba, the potential difference .DELTA.V.sub.12(g)
for the gray level g has a constant voltage, V.sub.b; and (iii)
when the gray level g is in the range from g.sub.b to R, the
potential difference .DELTA.V.sub.12(g) for the gray level g has a
constant voltage, V.sub.c. g=0, 1, 2, . . . , R corresponding to
one of the shades of grey of the image expressed in h bits, h is an
integer greater than zero and R=(2.sup.h-1). Additionally,
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero, and V.sub.a>V.sub.b>V.sub.c.
In yet a further aspect, the present invention relates to an LCD
panel. In one embodiment, the LCD panel includes a plurality of
pixels, {P.sub.n,m}, spatially arranged in the form of a matrix,
n=1, 2, . . . , N, and m=1, 2, . . . , M, and N, M being an integer
greater than zero, each pixel P.sub.n,m comprising at least a first
sub-pixel, P.sub.n,m(1), having a sub-pixel electrode and a second
sub-pixel, P.sub.n,m(2), having a sub-pixel electrode. In one
embodiment, the plurality of pixels, {P.sub.n,m}, is configured
such that when a gray level voltage associated with a gray level,
g, of an image to be displayed on a pixel is applied to the pixel
P.sub.n,m, a potential difference, .DELTA.V.sub.12(g), is generated
in the sub-pixel electrodes of the first and second sub-pixels of
the pixel P.sub.n,m, which varies with the gray level g of the
image to be displayed on the pixel, where g=0, 1, 2, . . . , R
corresponding to one of the shades of grey of the image expressed
in h bits, h being an integer greater than zero and
R=(2.sup.h-1).
In one embodiment, the potential difference .DELTA.V.sub.12(g)
generated in the sub-pixel electrodes of the first and second
sub-pixels of the pixel satisfies the following relationships of:
(1). when 0.ltoreq.g.ltoreq.g.sub.a,
.DELTA.V.sub.12(g)<.DELTA.V.sub.12(g+1); and (2). when
g.sub.b.ltoreq.g.ltoreq.R,
.DELTA.V.sub.12(g)>.DELTA.V.sub.12(g+1), where
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero.
In another embodiment, the potential difference .DELTA.V.sub.12(g)
satisfies the following relationships of: (i). when
0.ltoreq.g.ltoreq.g.sub.a, .DELTA.V.sub.12(g)=V.sub.a; (ii). when
g.sub.a.ltoreq.g.ltoreq.g.sub.b, .DELTA.V.sub.12(g)=V.sub.b; and
(iii). when g.sub.b.ltoreq.g.ltoreq.R, .DELTA.V.sub.12(g)=V.sub.c,
where 0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each
being an integer greater than zero, and V.sub.a, V.sub.b and
V.sub.c are constant voltages with
V.sub.a>V.sub.b>V.sub.c.
In one aspect, the present invention relates to a method of driving
a liquid crystal display (LCD) with color washout improvement. In
one embodiment, the method includes the steps of providing an LCD
panel comprising a plurality of pixels, {P.sub.n,m}, spatially
arranged in the form of a matrix, n=1, 2, . . . , N, and m=1, 2, .
. . , M, and N, M being an integer greater than zero, each pixel
P.sub.n,m comprising at least a first sub-pixel, P.sub.n,m(1),
having a sub-pixel electrode, and a second sub-pixel, P.sub.n,m(2),
having a sub-pixel electrode; and applying a plurality of driving
signals to the LCD panel so as to generate potential difference,
.DELTA.V.sub.12(g), in the sub-pixel electrodes of the first and
second sub-pixels of each pixel, respectively, which varies with a
gray level g of an image to be displayed on the pixel, where g=0,
1, 2, . . . , R corresponding to one of the shades of grey of the
image expressed in h bits, h being an integer greater than zero and
R=(2.sup.h-1).
In one embodiment, the potential difference .DELTA.V.sub.12(g)
generated in the sub-pixel electrodes of the first and second
sub-pixels of the pixel satisfies the following relationships of:
(1). when 0.ltoreq.g.ltoreq.g.sub.a,
.DELTA.V.sub.12(g)<.DELTA.V.sub.12(g+1); and (2). when
g.sub.b.ltoreq.g.ltoreq.R,
.DELTA.V.sub.12(g)>.DELTA.V.sub.12(g+1), where
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero.
In another embodiment, the potential difference .DELTA.V.sub.12(g)
satisfies the following relationships of: (ii). when
0.ltoreq.g.ltoreq.g.sub.a, .DELTA.V.sub.12(g)=V.sub.a; (iii). when
g.sub.a.ltoreq.g.ltoreq.g.sub.b, .DELTA.V.sub.12(g)=V.sub.b; and
(iv). when g.sub.b.ltoreq.g.ltoreq.R, .DELTA.V.sub.12(g)=V.sub.c,
where 0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each
being an integer greater than zero, and V.sub.a, V.sub.b and
V.sub.c are constant voltages with
V.sub.a>V.sub.b>V.sub.c.
These and other aspects of the present invention will become
apparent from the following description of the preferred embodiment
taken in conjunction with the following drawings, although
variations and modifications therein may be affected without
departing from the spirit and scope of the novel concepts of the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate one or more embodiments of the
invention and, together with the written description, serve to
explain the principles of the invention. Wherever possible, the
same reference numbers are used throughout the drawings to refer to
the same or like elements of an embodiment, and wherein:
FIG. 1 partially shows schematically an equivalent circuit diagram
of an LCD panel according to one embodiment of the present
invention;
FIG. 2 shows schematically (a) waveform charts of driving signals
applied to an LCD panel according to one embodiment of the present
invention, and (b) a layout view of the LCD panel, where the
transistors electrically connected to the gate lines G.sub.1 and
G.sub.2 are turned on, and the transistors electrically connected
to the gate line G.sub.3 are turned off, respectively;
FIG. 3 shows schematically (a) waveform charts of driving signals
applied to the LCD panel shown in FIG. 2b, and (b) the layout view
of the LCD panel, where the transistors electrically connected to
the gate line G.sub.1 are turned on, and the transistors
electrically connected to the gate lines G.sub.2 and G.sub.3 are
turned off, respectively;
FIG. 4 shows schematically (a) waveform charts of driving signals
applied to the LCD panel shown in FIG. 2b, and (b) the layout view
of the LCD panel, where the transistors electrically connected to
the gate line Glare turned off, and the transistors electrically
connected to the gate lines G.sub.2 and G.sub.3 are turned on,
respectively;
FIG. 5 shows schematically (a) waveform charts of driving signals
applied to the LCD panel shown in FIG. 2b, and (b) the layout view
of the LCD panel, where the transistors electrically connected to
the gate lines G.sub.1 and G.sub.3 are turned off, and the
transistors electrically connected to the gate line G.sub.2 are
turned on, respectively;
FIG. 6 shows the relationship of voltages of the first and second
sub-pixel electrodes of a pixel of an LCD panel and the grey level
for an image to be displayed on the pixel of the LCD panel
according to one embodiment of the present invention, (a) a
simulation result, and (b) an experimental result;
FIG. 7 shows the relationship of voltages of the first and second
sub-pixel electrodes of the pixel of the LCD panel according to the
embodiment of the present invention in FIG. 6, (a) a simulation
result, and (b) an experimental result;
FIG. 8 shows the relationship of the voltage difference in the
first and second sub-pixel electrodes of the pixel of the LCD panel
and the grey level for an image to be displayed on the pixel of the
LCD panel according to the embodiment of the present invention in
FIG. 6, (a) a simulation result, and (b) an experimental
result;
FIG. 9 shows the gamma curve the LCD panel according to the
embodiment of the present invention in FIG. 6, (a) a simulation
result, and (b) an experimental result;
FIG. 10 shows a simulation result of the relationship of voltages
of the first and second sub-pixel electrodes of a pixel of an LCD
panel and the grey level for an image to be displayed on the pixel
of the LCD panel according to one embodiment of the present
invention;
FIG. 11 shows a simulation result of the relationship of voltages
of the first and second sub-pixel electrodes of the pixel of the
LCD panel according to the embodiment of the present invention in
FIG. 10;
FIG. 12 shows a simulation result of the relationship of the
voltage difference in the first and second sub-pixel electrodes of
the pixel of the LCD panel and the grey level for an image to be
displayed on the pixel of the LCD panel according to the embodiment
of the present invention in FIG. 10; and
FIG. 13 shows a simulation result of the gamma curve the LCD panel
according to the embodiment of the present invention in FIG.
10.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is more particularly described in the
following examples that are intended as illustrative only since
numerous modifications and variations therein will be apparent to
those skilled in the art. Various embodiments of the invention are
now described in detail. Referring to the drawings, like numbers
indicate like components throughout the views. As used in the
description herein and throughout the claims that follow, the
meaning of "a", "an", and "the" includes plural reference unless
the context clearly dictates otherwise. Also, as used in the
description herein and throughout the claims that follow, the
meaning of "in" includes "in" and "on" unless the context clearly
dictates otherwise. Additionally, some terms used in this
specification are more specifically defined below.
As used herein, the terms "gamma" and/or "gamma curve" refer to the
characterization of brightness of an imaging display system, for
example, an LCD device, versus grey levels (scales). Gamma
summarizes, in a single numerical parameter, the nonlinear
relationship between grey level and brightness of the imaging
display system.
As used herein, the terms "grey level" and "grey scale" are
synonyms in the specification and refer to one of (discrete) shades
of grey for an image, or an amount of light perceived by a human
for the image. If the brightness of the image is expressed in the
form of shades of grey in h bits, n being an integer greater than
zero, the grey level takes values from zero representing black, up
to (2.sup.h-1) representing white, with intermediate values
representing increasingly light shades of grey. In an LCD device,
the amount of light that transmits through liquid crystals is
adjusted to represent the gray level.
As used herein, the term "grey level voltage" or "driving voltage"
refers to a voltage generated from a data driver in accordance for
driving a particular area or pixel of an LCD panel, in accordance
with a grey level of a frame of an image to be displayed at the
particular area or pixel of the LCD panel.
The terms "light transmittance/transmission", "brightness" and
"luminance", as used herein, are synonym in the specification and
refer to the amount of light that passes through a particular area
of an LCD panel.
It has been known that the orientations of liquid crystal molecules
in liquid crystal cells of an LCD panel play a crucial role in the
transmittance of light therethrough. For example, in a twist
nematic LCD, when the liquid crystal molecules are in its tilted
orientation, light from the direction of incidence is subject to
various different indexes of reflection. Since the functionality of
LCDs is based on the birefringence effect, the transmittance of
light will vary with different viewing angles. Due to such
differences in light transmission, optimum viewing of an LCD is
limited within a narrow viewing angle. Additionally, at different
grey levels, liquid crystals have different response times in an
LCD panel. For example, liquid crystals usually have the shortest
response time at the grey level 255, for 8-bit data signals for
example, compared to that at other grey levels. The difference
between the response times at different grey levels may result in
deviations of the gamma curves for different grey levels at
different areas of the LCD panel.
Therefore, one aspect of the present invention provides methods to
overcome the drawbacks of a color sequential LCD device.
The description will be made as to the embodiments of the present
invention in conjunction with the accompanying drawings in FIGS.
1-13. In accordance with the purposes of this invention, as
embodied and broadly described herein, this invention, in one
aspect, relates to an LCD panel with color washout improvement. In
one embodiment, the LCD panel includes a plurality of pixels
spatially arranged in the form of a matrix. Each pixel includes at
least a first sub-pixel having a sub-pixel electrode and a second
sub-pixel having a sub-pixel electrode. The plurality of pixels is
configured such that when a gray level voltage associated with a
gray level, g, of an image to be displayed on a pixel is applied to
the pixel, a potential difference is generated in the sub-pixel
electrodes of the first and second sub-pixels of the pixel, which
varies with the gray level g of the image to be displayed on the
pixel, where g=0, 1, 2, . . . , (2.sup.h-1) corresponding to one of
the shades of grey of the image expressed in h bits, h being an
integer greater than zero. That is the potential difference in the
sub-pixel electrodes of the first and second sub-pixels of the
pixel that results in different alignments of the LC molecules in
the first and second sub-pixels of the pixel, thereby improving
color washout of the LCD panel.
Referring to FIG. 1, an LCD panel according to one embodiment of
the present invention is partially and schematically shown. The LCD
panel 100 includes a common electrode 160, a plurality of scanning
lines, G.sub.1, G.sub.2, . . . , G.sub.n-1, G.sub.n, G.sub.n+1, . .
. , G.sub.N, that are spatially arranged along a row (scanning)
direction 130, and a plurality of data lines, D.sub.1, D.sub.2, . .
. , D.sub.m-1, D.sub.m, D.sub.m+1, . . . , D.sub.M, that are
spatially arranged crossing the plurality of scanning lines
G.sub.1, G.sub.2, . . . , G.sub.n-1, G.sub.n, G.sub.n+1, . . . ,
G.sub.N along a column direction 140 that is perpendicular to the
row direction 130. N and M are integers greater than one. The LCD
panel 100 further has a plurality of pixels, {P.sub.n,m}, 110 that
are spatially arranged in the form of a matrix. Each pixel
P.sub.n,m 110 is defined between two neighboring scanning lines
G.sub.n and G.sub.n+1 and two neighboring data lines D.sub.m and
D.sub.m+1. For the purpose of illustration of embodiments of the
present invention, FIG. 1 schematically shows only four scanning
lines G.sub.n-1, G.sub.n, G.sub.n+1 and G.sub.n+2, two data lines
D.sub.m and D.sub.m+1, and three corresponding pixels of the LCD
panel 100.
Furthermore, each pixel P.sub.n,m 110 is configured to have two or
more sub-pixels. As shown in FIG. 1, a pixel P.sub.n,m 110 located,
for example, between two neighboring scanning lines G.sub.n and
G.sub.n+1 and two neighboring data lines D.sub.m and D.sub.m+1
crossing the two neighboring scanning lines G.sub.n and G.sub.n+1
has a first sub-pixel, P.sub.n,m(1), 111a and a second sub-pixel,
P.sub.n,m(2), 111b. Each of the first sub-pixel P.sub.n,m(1) 111a
and the second sub-pixel P.sub.n,m(2) 111b comprises a sub-pixel
electrode 115a/115b, a liquid crystal (LC) capacitor 113a/113b and
a storage capacitor 114a/114b, and a transistor 112/116. Each pixel
is capable of displaying h bits of image data.
Both the LC capacitor 113a and the storage capacitor 114a of the
first sub-pixel P.sub.n,m(1) 111a of the pixel P.sub.n,m 110 are
electrically connected between the sub-pixel electrode 115a of the
first sub-pixel P.sub.n,m(1) 111a of the pixel P.sub.n,m 110 and
the common electrode 160 in parallel. The transistor 112 of the
first sub-pixel P.sub.n,m(1) 111a of the pixel P.sub.n,m 110 has a
gate 112g electrically connected to the scanning line G.sub.n, a
source 112s electrically connected to the sub-pixel electrode 115a
of the first sub-pixel P.sub.n,m(1) 111a of the pixel P.sub.n,m 110
and a drain 112d electrically connected to the data line D.sub.m.
The sub-pixel electrode 115a of the first sub-pixel P.sub.n,m(1)
111a of the P.sub.n,m 110 is in turn electrically connected to the
drain 116d of the transistor 116 of the second sub-pixel
P.sub.n+1,m (2) of the pixel P.sub.n+1,m.
Furthermore, both LC capacitor 113b and the storage capacitor 114b
of the second sub-pixel P.sub.n,m(2) 111b of the pixel P.sub.n,m
110 are electrically connected between the sub-pixel electrode 115b
of the second sub-pixel P.sub.n,m(2) 111b of the pixel P.sub.n,m
110 and the common electrode 160 in parallel. The transistor 116 of
the second sub-pixel P.sub.n,m(2) 111b of the pixel P.sub.n,m 110
has a gate 116g electrically connected to the scanning line
G.sub.n, a source 116s electrically connected to the sub-pixel
electrode 115b of the second sub-pixel P.sub.n,m(2) 111b of the
pixel P.sub.n,m 110 and a drain 116d electrically connected to the
sub-pixel electrode 115a of the first sub-pixel P.sub.n-1,m(1) of
the pixel P.sub.n-1,m.
In one embodiment, the sub-pixel electrodes 115a/115b of the first
sub-pixel P.sub.n,m(1) 111a and the second sub-pixel P.sub.n,m(2)
111b of each pixel P.sub.n,m 110 are deposited on a first substrate
(not shown), while the common electrode 160 is deposited on a
second substrate (not shown) that is spatially apart from the first
substrate. The LC molecules are filled into cells between the first
and second substrates. Each cell is associated with a pixel
P.sub.n,m 110 of the LCD panel 100. Voltages (potentials) applied
to the sub-pixel electrodes control orientational alignments of the
LC molecules in the LC cells associated with the corresponding
sub-pixels.
The transistor 112 and the transistor 116 in one embodiment are
field-effect TFTs and adapted for activating the first sub-pixel
P.sub.n,m(1) 111a and the second sub-pixel P.sub.n,m(2) 111b,
respectively. Other types of transistors may also be utilized to
practice the present invention. When the transistor 112 and the
transistor 116 are selected to be turned on by a scanning signal
applied through the scanning line G.sub.n to which the gate 112g of
the transistor 112 and the gate 116g of the transistor 116 are
electrically coupled, a data signal applied through the
corresponding data line D.sub.m is incorporated into the first
sub-pixel P.sub.n,m(1) 111a and the second sub-pixel P.sub.n,m(2)
111b by means of charging the corresponding LC capacitors 113a and
113b, and storage capacitors 114a and 114b of the first sub-pixel
P.sub.n,m(1) 111a and the second sub-pixel P.sub.n,m(2) 111b,
respectively. The charged potentials of the LC capacitors 113a and
113b of the first and second sub-pixels 111a and 111b of the pixel
110 are corresponding to the electrical fields applied to
corresponding liquid crystal cells between the first and second
substrates. The storage capacitor 114a and the storage capacitor
114b are adapted for providing coupling voltages to the
corresponding LC capacitors 113a and 113b, respectively, to
compensate for charge leakages therefrom. The storage capacitors
114a and 114b of the first and second sub-pixels 111a and 111b can
be identical or different.
In one embodiment, the driving signals include a plurality of
scanning signals, a plurality of data signals and a common signal.
For such an LCD panel 100 shown in FIG. 1, when a scanning signal
is applied to a scanning line G.sub.n to turn on the corresponding
transistors 112 and 116 connected to the scanning line G.sub.n, a
plurality of data signals is simultaneously applied to the
plurality of data lines {D.sub.n} so as to charge the corresponding
LC capacitors 113a and 113b and storage capacitors 114a and 114b of
each pixel P.sub.n,m 110 of the corresponding pixel row for
aligning states of corresponding liquid crystal cells associated
with the first and second sub-pixels P.sub.n,m(1) 111a and
P.sub.n,m(2) 111b of the pixel P.sub.n,m 110 to control light
transmittance therethrough. Accordingly, the voltage, Vp1,
generated in the sub-pixel electrode 115a of the first sub-pixel
P.sub.n,m(1) and the voltage, Vp2, generated in the sub-pixel
electrode 115b of the second sub-pixel P.sub.n,m(2) of the
P.sub.n,m are different, due to the coupling between the sub-pixel
electrode 115a of the first sub-pixel P.sub.n,m(1) of the P.sub.n,m
to the sub-pixel electrode 115b of the second sub-pixel
P.sub.n+,m(2) of the P.sub.n+1,m. In other words, the LC molecules
associated with the first sub-pixel P.sub.n,m(1) and the second
sub-pixel P.sub.n,m(2) of the P.sub.n,m may be aligned at different
orientations responsive to a voltage difference,
.DELTA.V.sub.12=(Vp2-Vp1), in the sub-pixel electrode 115a of the
first sub-pixel P.sub.n,m(1) and the sub-pixel electrode 115b of
the second sub-pixel P.sub.n,m(2) of the P.sub.n,m.
Practically, the plurality of data signals includes a plurality of
gray level voltages. Each gray level voltage is associated with a
gray level, g, of an image to be displayed on a pixel P.sub.n,m.
g=0, 1, 2, . . . , R corresponding to one of the shades of grey of
the image expressed in h bits, h being an integer greater than zero
and R=(2.sup.h-1). When such a gray level voltage is applied the
pixel P.sub.n,m, the potential difference
.DELTA.V.sub.12(g)=(Vp2-Vp1) in the sub-pixel electrodes of the
first and second sub-pixels of the pixel is generated, and varies
with the gray level g. In one embodiment, the potential difference
.DELTA.V.sub.12(g) in the sub-pixel electrodes 115a and 115b of the
first sub-pixel P.sub.n,m(1) and the second sub-pixel P.sub.n,m(2)
of the pixel P.sub.n,m satisfies the following relationships of:
(1). when 0.ltoreq.g.ltoreq.g.sub.3,
.DELTA.V.sub.12(g)<.DELTA.V.sub.12(g+1); and (2). when
g.sub.b.ltoreq.g.ltoreq.R,
.DELTA.V.sub.12(g)>.DELTA.V.sub.12(g+1), where
0.ltoreq.g.ltoreq.g.sub.b<R, g.sub.3 and g.sub.b each being an
integer greater than zero.
In another embodiment, the potential difference .DELTA.V.sub.12(g)
satisfies the following relationships of: (i). when
0.ltoreq.g.ltoreq.g.sub.3, .DELTA.V.sub.12(g)=V.sub.3; (ii). when
g.sub.a.ltoreq.g.ltoreq.g.sub.b, .DELTA.V.sub.12(g)=V.sub.b; and
(iii). when g.sub.b.ltoreq.g.ltoreq.R, .DELTA.V.sub.12(g)=V.sub.c,
where 0.ltoreq.g.ltoreq.g.sub.b.ltoreq.R, g.sub.3 and g.sub.b each
being an integer greater than zero, and V.sub.3, V.sub.b and
V.sub.c are constant voltages with
V.sub.3>V.sub.b>V.sub.c.
Another aspect of the present invention relates to an LCD panel
having a common electrode, a plurality of scanning lines, G.sub.1,
G.sub.2, . . . , G.sub.n-1, G.sub.n, G.sub.n+1, . . . , G.sub.N,
that are spatially arranged along a scanning direction, and a
plurality of data lines, D.sub.1, D.sub.2, . . . D.sub.m-1,
D.sub.m, D.sub.m+1, . . . , D.sub.M, that are spatially arranged
crossing the plurality of scanning lines G.sub.1, G.sub.2, . . . ,
G.sub.n-1, G.sub.n, G.sub.n+1, . . . , G.sub.N along a direction
that is perpendicular to the scanning direction, and a plurality of
pixels, {P.sub.n,m}, that are spatially arranged in the form of a
matrix. N and M are integers greater than one. Each pixel P.sub.n,m
includes at least a first sub-pixel P.sub.n,m(1) and a second
sub-pixel P.sub.n,m(2). Each of the first sub-pixel P.sub.n,m(1)
and the second sub-pixel P.sub.n,m(2) comprises a sub-pixel
electrode, a liquid crystal (LC) capacitor and a storage capacitor
both electrically connected between the sub-pixel electrode and the
common electrode in parallel, and a transistor having a gate
electrically connected to the scanning line G.sub.n, a source
electrically connected to the sub-pixel electrode and a drain.
In one embodiment, the drain of the transistor of the first
sub-pixel P.sub.n,m(1) of the pixel P.sub.n,m is electrically
connected to the data line D.sub.m, and the drain of the transistor
of the second sub-pixel P.sub.n,m(2) of the pixel P.sub.n,m is
electrically connected to the sub-pixel electrode of the first
sub-pixel P.sub.k,m(1) of the pixel P.sub.k,m, where k=1, 2, . . .
, N, and k.noteq.n. For the exemplary embodiment shown in FIG. 1,
k=n-1.
In another embodiment, the drain of the transistor of the second
sub-pixel P.sub.n,m(2) of the pixel P.sub.n,m is electrically
connected to the data line D.sub.m, and the drain of the transistor
of the first sub-pixel P.sub.n,m(1) of the pixel P.sub.n,m is
electrically connected to the sub-pixel electrode of the second
sub-pixel P.sub.k,m(2) of the pixel P.sub.k,m, where k=1, 2, N, and
k.noteq.n.
Referring to FIGS. 2-5, waveform charts of the driving signals 201
applied to the LCD panel 200 and charging in the corresponding
sub-pixel electrodes 215a and 215b of the LCD panel 200 are shown
according to one embodiment of the present invention. In the
exemplary embodiment, the LCD panel 200 is shown schematically and
partially with 3.times.3 pixels, where the pixels, for example, in
the first column of the 3.times.3 pixel matrix are referenced by
P.sub.1,1, P.sub.2,1 and P.sub.3,1, respectively. Each pixel has a
first sub-pixel electrode 215a, a second sub-pixel electrode 215b,
a first transistor (switching device) 211 and a second transistor
(switching device) 216, each transistor 211 or 216 having a gate, a
source and a drain. The gates of both the first transistor 211 and
the second transistor 216 of each pixel are electrically connected
to a corresponding scanning line by which the pixel is defined,
such as G.sub.1, G.sub.2 or G.sub.3. The sources of the first
transistor 211 and the second transistor 216 of each pixel are
electrically connected to the first sub-pixel electrode 215a and
the second sub-pixel electrode 215b of the pixel, respectively. The
drain of the second transistor 216 of each pixel is electrically
connected to a corresponding data line by which the pixel is
defined, such as D.sub.1 or D.sub.2, and the drain of the first
transistor 212 of each pixel is electrically connected to the
sub-electrode 215b of its next neighboring pixel in the same column
of the pixel. For example, the drain of the first transistor 212 of
the pixel P.sub.1, is electrically connected to the sub-electrode
215b of the pixel P.sub.2,1, the drain of the first transistor 212
of the pixel P.sub.2,1 is electrically connected to the
sub-electrode 215b of the pixel P.sub.3,1, and so on, as shown in
FIGS. 2-5.
In the exemplary embodiment, the driving signals 201 include three
scanning signals 271, 272 and 273 sequentially applied to the
scanning lines G.sub.1, G.sub.2 and G.sub.3, and two data signals
281 and 282 simultaneously applied to the data lines D.sub.1 and
D.sub.2, and a common signal Vcom 290 applied to the common
electrode (not shown), respectively. Each of the scanning signals
271, 272 and 273 is configured to have a high voltage potential,
Vh, and a low voltage potential, Vl, for effectively turning on and
off the corresponding transistors of a corresponding pixel row. The
common signal Vcom 290 has a constant potential (voltage). The data
signals 281 and 282 are generated according to an image to be
displayed on these pixels such that when the data signals 281 and
282 are applied to corresponding pixels, a potential (voltage)
difference between the potentials of the first and second
electrodes 215a and 215b of a pixel is generated. The potential
difference is a function of the grey level for the image to be
displayed.
As shown in FIG. 2, in the time period 221 of (t1-t0), the
transistors 212 and 216 electrically connected to the scanning
lines G.sub.1 and G.sub.2 are turned on, while the transistors 212
and 216 electrically connected to the scanning line G.sub.2 are
turned off, respectively. Accordingly, a potential (voltage), Vp2,
of the second sub-pixel electrode 215b of the pixels P.sub.1, and
P.sub.2,1 is generated directly by application of the data signal
281 to the drain of the second transistor 216 of the pixels
P.sub.1, and P.sub.2,1, respectively, while a potential (voltage),
Vp1, of the first electrode 215a of the pixel P.sub.1,1 is
generated by application of the generated voltage Vp2 of the second
sub-pixel electrode 215b of the pixel P.sub.2,1 to the drain of the
first transistor 212 of the pixel P.sub.1,1. The latter charging
process is indicated by arrow 218a. In this case, the voltage
difference, .DELTA.V12=Vp2-Vp1 is generated in the first and second
electrodes 215a and 215b of the pixel P.sub.1,1.
In the time period 222 of (t2-t1), as shown in FIG. 3, the
transistors 212 and 216 electrically connected to the scanning line
G.sub.1 are turned on, while the transistors 212 and 216
electrically connected to the scanning lines G.sub.2 and G.sub.3
are turned off, respectively. Accordingly, a voltage, Vp2, of the
second sub-pixel electrode 215b of the pixel P.sub.1, is generated
directly by application of the data signal 281 to the drain of the
second transistor 216 of the pixel P.sub.1,1, while no voltage of
the first electrode 215a of the pixel P.sub.1, is generated since
the transistor 216 of the pixel P.sub.2,1 is turned off. The
charging process of the second electrode 215b of the pixel P.sub.1,
is indicated by arrow 218b. Accordingly, the voltage difference,
.DELTA.V12, in the first and second electrodes 215a and 215b of the
pixel P.sub.1,1 is corresponding to Vp2.
As shown in FIG. 4, in the time period 223 of (t3-t2), the
transistors 212 and 216 electrically connected to the scanning
lines G.sub.2 and G.sub.3 are turned on, while the transistors 212
and 216 electrically connected to the scanning line G.sub.1 are
turned off, respectively. Accordingly, a potential (voltage), Vp2,
of the second sub-pixel electrode 215b of the pixels P.sub.2,1 and
P.sub.3,1 is generated directly by application of the data signal
281 to the drain of the second transistor 216 of the pixels
P.sub.2,1 and P.sub.3,1, respectively, while a potential (voltage),
Vp1, of the first electrode 215a of the pixel P.sub.2,1 is
generated by application of the generated voltage Vp2 of the second
sub-pixel electrode 215b of the pixel P.sub.3,1 to the drain of the
first transistor 212 of the pixel P.sub.2,1. The latter charging
process is indicated by arrow 218c. In this case, the voltage
difference, .DELTA.V12, in the first and second electrodes 215a and
215b of the pixel P.sub.2,1 is corresponding to (Vp2-Vp1).
In the time period 224 of (t4-t3), as shown in FIG. 5, the
transistors 212 and 216 electrically connected to the scanning line
G.sub.2 are turned on, while the transistors 212 and 216
electrically connected to the scanning lines G.sub.1 and G.sub.3
are turned off, respectively. Accordingly, a voltage, Vp2, of the
second sub-pixel electrode 215b of the pixel P.sub.2,1 is generated
directly by application of the data signal 281 to the drain of the
second transistor 216 of the pixel P.sub.2,1, while no voltage of
the first electrode 215a of the pixel P.sub.2,1 is generated since
the transistor 216 of the pixel P.sub.3,1 is turned off. The
charging process of the second electrode 215b of the pixel
P.sub.2,1 is indicated by arrow 218d. Accordingly, the voltage
difference, .DELTA.V12, in the first and second electrodes 215a and
215b of the pixel P.sub.2,1 is corresponding to Vp2.
In the embodiment as shown in FIGS. 2-5, the first sub-pixel
electrode 215a of a pixel has an area A1 and the second sub-pixel
electrode 215b of the pixel has an area A2. The ratio of
.DELTA.1/A2 is in a range of about 0.2-5.0, in one embodiment.
Referring to FIG. 6, the simulation and experimental results for
the voltages Vp1 and Vp2 of the first and second sub-pixel
electrodes of a pixel of an LCD panel against the grey level for an
image to be displayed on the pixel of the LCD panel are shown
according to one embodiment of the present invention, where the
area ratio of A1/A2=1/1.6, and the grey level is expressed in an 8
bit. In FIG. 6, Vp'1=(Vp1-Vcom), and Vp'2=(Vp2-Vcom), where Vcom is
the voltage applied to the common electrode. The voltage difference
in the first and second sub-pixel electrodes of the pixel is
.DELTA.V12=(Vp'2-Vp'1)=(Vp2-Vp1). FIG. 7 shows the simulation and
experimental results for the voltages Vp1 and Vp2 of the first and
second sub-pixel electrodes of the pixel of the LCD panel according
to the embodiment of the present invention in FIG. 6. In this
embodiment, the first sub-pixel electrode has a lower voltage and a
larger area, comprising with those of the sub-pixel electrode.
Accordingly, the voltage difference .DELTA.V12 in the first and
second sub-pixel electrodes of the pixel varies with the grey
level, as shown in FIG. 8. When the grey level g increases from 0
to g.sub.a, the voltage difference .DELTA.V12 increases, i.e.,
.DELTA.V12(g)<.DELTA.V12(g+1), for 0.ltoreq.g.ltoreq.g.sub.a,
while the voltage difference .DELTA.V12 decreases as the grey level
g increases from g.sub.b to R=255, i.e.,
.DELTA.V.sub.12(g)>.DELTA.V.sub.12(g+1) for
g.sub.b.ltoreq.g.ltoreq.R. Both g.sub.a and g.sub.b that is larger
than g.sub.a are larger than zero but less than R, and may vary
with the characteristic of the liquid crystals and the area ratio
of the first sub-pixel electrode to the second sub-pixel
electrode.
FIG. 9 shows the simulation and experimental results of the gamma
curve of the LCD panel, where Gamma_0 is set to be 2.4 and the
first sub-pixel electrode has a lower voltage and a larger area,
comprising with those of the sub-pixel electrode. For the
simulation of the gamma curve, as shown in FIG. 9a, the area ratio
of A1/A2=1/1.6, while the area ratio of A1/A2=1/1.2 for the
experiment result of the gamma curve, as shown in FIG. 9b. In the
simulation of the gamma curve, the driving signals are configured
such that when the grey level g is in the range of 0-96, the first
sub-pixel transmits no light, or a little amount of light, where
the gamma curve in this range of the grey level is indicated by
reference numeral 910, while the first sub-pixel transmits a large
amount of light when the grey level g is greater than 96.
Furthermore, when the grey level g is in the range of 176-255, the
second sub-pixel transmits the most amount of light, where the
gamma curve in this range of the grey level is indicated by
reference numeral 920. The brightness of the second sub-pixel is
reduced for g<176.
FIGS. 10 and 12 respectively show the simulation result for the
voltages Vp1 and Vp2 of the first and second sub-pixel electrodes
of a pixel of an LCD panel and its voltage difference
.DELTA.V12=(Vp2-Vp1) against the grey level for an image to be
displayed on the pixel of the LCD panel are shown according to
another embodiment of the present invention. It is clear that the
voltage difference .DELTA.V12 in the first and second electrodes of
a pixel varies with the grey level g. In this embodiment,
.DELTA.V.sub.12(g)=V.sub.a for 0.ltoreq.g.ltoreq.g.sub.a,
.DELTA.V.sub.12(g)=V.sub.b for g.sub.a.ltoreq.g.ltoreq.g.sub.b, and
.DELTA.V.sub.12(g)=V.sub.c for g.sub.b.ltoreq.g.ltoreq.R=255, where
V.sub.a=1.2V, V.sub.b=1.1V and V.sub.c=0.8V. FIG. 11 shows the
simulation for the voltages Vp1 and Vp2 of the first and second
sub-pixel electrodes of the pixel of the LCD panel. FIG. 13 shows
the simulation of the gamma curve of the LCD panel.
One aspect of the present invention provides a method of improving
color washout of an LCD device. In one embodiment, the method
includes the step of providing an LCD panel having a plurality of
pixels, {P.sub.n,m}, spatially arranged in the form of a matrix,
n=1, 2, . . . , N, and m=1, 2, . . . , M, and N, M being an integer
greater than zero. Each pixel P.sub.n,m has at least a first
sub-pixel, P.sub.n,m(1), having a sub-pixel electrode and a second
sub-pixel, P.sub.n,m(2), having a sub-pixel electrode, The method
also includes the step of applying a plurality of driving signals
to the LCD panel so as to generate potential difference,
.DELTA.V.sub.12(g), in the sub-pixel electrodes of the first and
second sub-pixels of each pixel, respectively, which varies with a
gray level g of an image to be displayed on the pixel, where g=0,
1, 2, . . . , R corresponding to one of the shades of grey of the
image expressed in h bits, h being an integer greater than zero and
R=(2.sup.h-1).
In one embodiment, the potential difference .DELTA.V.sub.12(g)
generated in the sub-pixel electrodes of the first and second
sub-pixels of a pixel varies with the gray level g, such that (i)
when the gray level g is in the range from 0 to g.sub.a, the
potential difference .DELTA.V.sub.12(g) for the gray level g is
less than the potential difference .DELTA.V.sub.12(g+1) for the
gray level (g+1); and (ii) when the gray level g is in the range
from g.sub.b to R, the potential difference .DELTA.V.sub.12(g) for
the gray level g is greater than the potential difference
.DELTA.V.sub.12(g+1) for the gray level (g+1), where
0<g.sub.a.ltoreq.g.sub.b<R, g.sub.a and g.sub.b each being an
integer greater than zero.
In another embodiment, the potential difference .DELTA.V.sub.12(g)
varies with the gray level g, such that (i) when the gray level g
is in the range from 0 to g.sub.a, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.a; (ii) when the gray level g is in the range from g.sub.a to
g.sub.b, the potential difference .DELTA.V.sub.12(g) for the gray
level g has a constant voltage, V.sub.b; and (iii) when the gray
level g is in the range from g.sub.b to R, the potential difference
.DELTA.V.sub.12(g) for the gray level g has a constant voltage,
V.sub.c, where V.sub.a>V.sub.b>V.sub.c.
The foregoing description of the exemplary embodiments of the
invention has been presented only for the purposes of illustration
and description and is not intended to be exhaustive or to limit
the invention to the precise forms disclosed. Many modifications
and variations are possible in light of the above teaching.
The embodiments were chosen and described in order to explain the
principles of the invention and their practical application so as
to activate others skilled in the art to utilize the invention and
various embodiments and with various modifications as are suited to
the particular use contemplated. Alternative embodiments will
become apparent to those skilled in the art to which the present
invention pertains without departing from its spirit and scope.
Accordingly, the scope of the present invention is defined by the
appended claims rather than the foregoing description and the
exemplary embodiments described therein.
* * * * *